This invention relates to a vane compressor for compressing refrigerant circulating through an air-conditioner for automotive vehicles or the like.
Conventionally, a vane compressor of this kind has been disclosed, e.g., by Japanese Provisional Publication (Kokai) No. 59-176492 (Japanese Patent Publication (Kokoku) No. 1-21358), in which, as shown in FIG. 1, each vane back pressure chamber 113a communicates with a discharge pressure chamber 110 via an annular groove 134, an internal clearance in a radial roller bearing 109 supporting a driving shaft 120, a through hole 109b formed through the outer race of the roller bearing 109, and a passage 136 formed in a side block 102. Arranged in the passage 136 is a valve 141 which opens the passage 136 when the pressure of refrigerant gas within the discharge pressure chamber 110 is lower than a predetermined value, and closes same when the same pressure is higher than the predetermined value.
Even if the centrifugal force acting upon the vane 114 is small and the back pressure within the vane back pressure chamber 113a is not high enough at the start of the compressor, the vane 114 retracted within the associated vane slit 113 is projected out of same as the rotor 102 rotates, since refrigerant gas is supplied to the vane back pressure chamber 113a via the passage 136, the through hole 109b, the internal clearance of the roller bearing 109, and the annular groove 134. Thus, the vane is urged against the inner peripheral surface of a cam ring 101 to start the operation of the compressor without chattering of the vanes and hence occurrence of noise, etc.
Another vane compressor has been disclosed, e.g., by Japanese Provisional Patent Publication (Kokai) No. 56-107992, in which, as shown in FIG. 2, a groove (not shown) opposed to vane back pressure chambers (not shown) is formed in an end face of a side block 151 facing the rotator 161. The vane back pressure chamber communicates with a discharge refrigerant passage 153, through which refrigerant gas compressed by a compression chamber 155 is fed, via a passage 152 formed through the side block 151. Provided in the passage 152 is a valve 154 which opens the passage 152 when a differential pressure between pressure in the discharge refrigerant passage 153 and pressure in the groove is below a predetermined value, and closes same when the differential pressure is above the predetermined value. At the start of the compressor, each vane 157 is easily projected out of the associated vane slit (not shown) since refrigerant gas is introduced into the vane back pressure chamber from the discharge refrigerant passage 153 via the passage 152. Therefore, it is possible to prevent a phenomenon that at the start of the compressor the groove and the vane slits are sealed to hinder the vanes from projecting out of the vane slits.
However, in the vane compressor of FIG. 1, lubricating oil gathered in the roller bearing 109 flows into the passage 136 via the through hole 109b to sometimes block same up. On the other hand, in the vane compressor of FIG. 2, lubricating oil introduced into the roller bearing 160 via a passage 158 and a through hole 159 is collected in the groove through a clearance between the side block 151 and the rotor 161. The lubricating oil collected in the groove may flow into the passage 152 to sometimes block same up. If the passages 136, 152 in FIGS. 1 and 2 are blocked up, negative pressure is generated within the vane back pressure chambers at the bottom of the vane slits when the vanes are projected out of the respective vane slits. Therefore, at the start of operation of the compressor, during which the centrifugal force acting upon the vanes is small, the vanes can be hardly projected out of the vane slits to cause chattering of the vanes. Particularly when the outside air temperature is low, this phenomenon occurs frequently. The phenomenon has occurred more frequently due to the use of a lubricating oil having higher viscosity to cope with the recent use of aluminum or an aluminum alloy as the material of the compressor.